Solar Power Could Make the Grid More Resilient
Richard Perez, Jeffrey Freedman, and James W. Fossett
Widespread, extended power outages are among the most damaging consequences of severe weather events. Power outages can compromise response efforts. They make it impossible for hospitals, transit systems, fuel distribution and other critical infrastructure to function. And they cause the loss of sales, employee income, and perishable inventories for pharmacies, hospitals, restaurants, grocery stores, and other businesses. Economic damage from power outages often extends across large regions. In the aftermath of Superstorm Sandy, for example, large areas of New York and New Jersey that were untouched by the storm surge experienced hurricane-force wind gusts, resulting in downed utility lines and power losses that lasted over a week. Even inland, away from hurricane conditions, severe weather can bring down power lines and leave large areas without power for significant periods of time. It has been estimated that severe weather-related power outages cost the American economy over $300 billion between 2003 and 2012.
Such wide-scale outages have increased significantly in recent years in the Northeast, which has emerged as a national “hot spot” for severe weather events. Extreme precipitation events in the Northeast have increased by 74 percent between 1958 and 2011. Nationally, the annual average number of power outages related to severe weather and affecting more than 50,000 customers doubled between 2003 and 2012. While large-scale weather related power outages are more common in other parts of the country, a group of six states in the Northeast experienced 67 large-scale power outages over this period, including the widespread power losses, affecting millions of people, associated with Superstorm Sandy. Moreover, under a variety of scenarios, precipitation in the Northeast by the end of the century is expected to increase by 20–30 percent over current levels, with a potential corresponding increase in extreme events associated with catastrophic flooding.
Given these forecasts, many Northeastern states are considering employing small-scale “microgrids” to add resiliency to power distribution systems by protecting against large-scale outages in the “macrogrid.” Microgrids are part of the larger grid during normal conditions, but they have independent power sources that can disconnect from the larger distribution system and continue to operate independently when the system goes down. They can be as small as a single residence or commercial building, or they can encompass neighborhoods, communities, military bases or university campuses. Several states — Massachusetts, Maryland, New Jersey, New York, and Connecticut — are actively pursuing the development of such community-based microgrids. Emergency response centers and other critical infrastructures and businesses are prime candidates for microgrid deployment as they must be operational at all times independently of the larger grid to maintain response capabilities and minimize the economic damage done by extended power outages.
The technical, economic, and regulatory issues involved in developing microgrids are intricate but not insurmountable. One issue attracting attention among policymakers and stakeholders is the potential role of solar power as an emergency source of electricity for microgrids. Solar powered microgrids may be more reliable than conventionally powered microgrids dependent on a supply of fossil fuels that may be disrupted by power outages. During Superstorm Sandy, fuel supplies were compromised for an extended period of time both by significant damage to the fuel delivery system as well as power outages, which made it impossible for gas pumps to operate. Two weeks after Sandy, product inflows and outflows in the New York Harbor area were less than two-thirds of pre-storm levels, leading to significant shortages.
By contrast, the potential disruption in solar “fuel” supply may be much less severe. Most outages are associated with transient severe events such as hurricanes, floods, snow/ice storms, and thunderstorm complexes that are typically followed by calmer weather. For example, Hurricane Irene, which caused unprecedented flooding and widespread power outages throughout upstate New York, was followed by three to four consecutive days of mostly clear skies throughout much of the state. Battery storage would further enhance reliability of these solar power systems. Moreover, emergency microgrids are intended to serve only a small number of critical electrical loads to keep facilities afloat during power outages. In hospitals, for example, these subsystems might include equipment in emergency rooms or neonatal intensive care units where patients are dependent for survival on specialized equipment. In most cases, these critical loads represent a small fraction of normal day-to-day loads, and therefore could be served indefinitely with solar microgrids.
Currently, microgrid-capable solar systems are uncommon. Most operating solar systems are of little value in an outage because they lack the ability to disconnect from the grid and continue to operate independently. During Superstorm Sandy, solar systems that were not physically destroyed by the storm — the overwhelming majority of them — survived very well and were back in operation as the grid re-energized. Had these systems been part of emergency microgrids, they could have supplied emergency power indefinitely during the outage.
Off-the-shelf “smart” technology exists that can operate solar microgrids, including automatically disconnecting and continuing operation in the event of an outage. With solar systems becoming increasingly competitive in price with traditional fuel sources — solar module prices have declined by 80 percent since 2008 — adding microgrid capability to solar systems could become an affordable priority. Some states and utilities are already investing in solar powered facilities along these lines, and companies are marketing “smart” solar systems to commercial buildings. The Army is also investing heavily in solar powered microgrids supplemented by batteries as a means of insuring continued power supply during grid outages.
Increasing the use of solar powered microgrids, in short, offers a reliable source of emergency power that has advantages over traditional sources and is increasingly competitive in price. Widespread deployment of such devices could maintain emergency response capabilities and minimize the economic damage done by large-scale, long-lasting power outages in the event of increasingly likely severe weather.